In the manufacture of reticulated structures, such as geodesic structures, it is desirable to be able to take advantage of the unique characteristics of advanced composite materials, such as thermosetting resins, having unidirectional filaments therein oriented parallel to the axis of discrete load paths in such structures. A multiple of laminate bars formed from fibers and resin laid in the above arrangement will result in a redundant structure, with the fibers being continuous and loads being transferred from one bar to another through shear at their intersections. One of the chief requirements in the design and fabrication of viable geodesic structures is the stabilization of the individual plies of the bars between the nodal intersections. If the structure is composed of two intersecting bars, each bar consisting of one or more alternately laid down plies, then there is a gap created between the plies in the bars between the nodal intersections equal in thickness to that of one ply. Similarly, if the structure is composed of three intersecting bars then there is a gap created between the plies in the bars equal in thickness to that of two plies. The resultant structure is thus unstable and also quite non-uniform in thickness. In order to manufacture a reticulated structure which is stable and which is substantially uniform in thickness, any resinous material used to fill the gaps between the plies comprising the bars must completely fill the gaps and must be absent at the nodal intersections. In addition, since the load bearing and transferring capabilities of such resinous material are necessarily low, the presence of such resinous material at the nodal intersections causes the reticulated structure to be substantially weaker. One technique which has been employed to fill the gaps between the plies of the bars between the nodal intersections has been the application of wet resin. It has been found, however, that the resin flows excessively during the process of manufacturing the geodesic structure and that a great many voids occur in the finished laminate arising during the curing cycle. A second technique which has been used is to insert strips of a resinous medium between the plies of the bars between the nodal intersections or to cut away the resinous medium at the intersections. The laying in or cutting away of this resinous medium, however, adds a costly hand-laying step to the fabrication process and also introduces compatibility problems into the cure cycle. It is also quite apparent that the above techniques for fabricating a reticulated structure using resinous materials do not lend themselves readily to continuous winding or tape-laying procedures.
Accordingly, it is a general object of the present invention to provide a resinous material suitable for the fabrication of laminated structures.
It is another object of the present invention to provide a resinous material suitable for the fabrication of reticulated structures having a substantially uniform thickness.
It is a further object of the present invention to provide a resinous materials which can be used in a winding or tape-laying process for the fabrication of reticulated structures having a substantially uniform nodal and internodal thickness.